Small update:
(1) I actually found another, so I have four of them right now.
(2) I also found four of correspondent 1 x 6" ProCap Copper Plate
So, currently I have
(four) 1 x 6" x 6" x 3" Stainless Steel Sight Glass Union Tee
(four) 1 x 6" ProCap Copper Plate
At Still Dragon, they are $245 for tee and $36 for plate each.
They are yours for $600 all together.
Thanks